This invention relates to a lubricating system and more particularly to a lubricating system for use with internal combustion engines.
As is well known, most mechanisms that have moving parts require some form of lubricating system. These lubricating systems all have in common the necessity of ensuring adequate lubricant for the components being lubricated for long time intervals without servicing and preventing leakage of the lubricant to the atmosphere.
Internal combustion engines are typical examples of mechanisms that require lubrication. The problems in lubricating engines are typical of those of other applications but in some instances the lubricating system for an engine is more demanding because of the likelihood of the lubricant escaping to the atmosphere. This is particularly true with respect to two-cycle internal combustion engines wherein the lubricant is not contained within a separate lubricant sump and recirculated through the engine during its operation as with four-cycle engines.
With two-cycle engines it is expected that some of the lubricant will escape to the atmosphere through the exhaust system since the lubricant is not normally recirculated through the engine. As a result of this difference, it is desirable to accurately control the amount of lubricant that is supplied to an engine and particularly to two-cycle engines. With such arrangements, it is necessary to insure that the components of the engine receive adequate lubricant for all running conditions but also that excess lubricant is not supplied. The excess lubricant can escape to the atmosphere or carbonize within the engine, each of which causes its own type of problem.
Various lubricating systems have been proposed for two-cycle engines and some of these systems also have application to four-cycle engines. For example, the lubrication of the connecting rod journals on the crankshaft is a particularly critical area. Arrangements have been provided for ensuring that lubricant is delivered to the crankshaft journals under all running conditions, particularly during startup. One system which has been proposed for this use is described in U.S. Pat. No. 4,969,430, entitled LUBRICATION SYSTEM FOR TWO-STROKE ENGINE, issued Nov. 14, 1990 in the name of Tatsuyuki Masuda and assigned to the assignee hereof.
In that patent, an arrangement is illustrated wherein oil is delivered from the main bearings to the connecting rod bearings through a transversely extending passage formed in the throws of the crankshaft. This transversely extending passage is intercepted by a radially extending passage that extends to the connecting rod journal. Although that system is very effective in that it employs the centrifugal force of the crankshaft as a means for assisting in delivering the lubricant, it does have areas that could be improved. For example, the transverse drilling through the throw is closed at its outer end by a plug and the radial drilling intersects the transverse drilling at some distance from this plug. Hence, on initial startup it is necessary to fill the void area between the plug and the cross drilling before a lubricant will be forced from the cross drilling to the connecting rod journal.
It is, therefore, a first object of this invention to provide an improved arrangement for lubricating the connecting rod journals of a reciprocating machine.
It is a further object of this invention to provide an improved arrangement for lubricating the connecting rod journals of a reciprocating machine wherein it will be insured that lubricant will be delivered to the journals immediately upon the machine's operation.
In conjunction with the lubrication of reciprocating machines, an area of high wear and one requiring adequate lubrication is the skirt of the piston. Various arrangements have been provided for lubricating piston skirts and in some of these arrangements there are passages drilled through the cylinder liner and through which lubricant is delivered to the piston skirt. It is necessary and desirable to insure that the lubricant that is delivery to the piston skirt will cover substantially the entire skirt's circumference at least in the highly loaded areas transverse to the piston pin axis.
It is, therefore, a still further object of this invention to provide an improved arrangement for lubricating the skirt of a piston of a reciprocating machine.
It is a further object of the invention to provide a piston construction wherein lubricant can be easily distributed over the sliding surfaces of the skirt.
In conjunction with the primary application of the engine, frequently it is also the practice to drive an air pump off of the engine. This air pump may be employed either for the internal operation of the engine or, in certain automotive applications, may be employed for external or vehicular purposes. For example, with certain types of engines such as diesel engines, the induction system of the engine does not generate large amounts of intake manifold vacuum. Many vehicle accessories, such as power brake systems, however, require a source of vacuum so as to have atmospheric pressure assist.
Where the engine is provided with an air pump, it is desirable to supply lubricant to the air pump as with the engine itself. Like the engine, however, the lubricant that is supplied to the air pump should not be permitted to be discharged back to the atmosphere nor, for that matter, should the lubricant which may become entrained in the air pumped by the air pump be permitted to be delivered to the source where the air is delivered.
It is, therefore, a still further object of this invention to provide an improved lubricating system for an air pump for an internal combustion engine wherein the lubricant is drawn from and returned to a lubricant sump contained within the engine.
In accordance with another object of the invention, it is an object to provide an arrangement for separating the lubricant supplied to an air pump from the air pumped before the air is delivered to the desired location in the engine.
Another type of mechanism which requires lubrication is a transmission. Transmissions comprised of intermeshing gears should be well lubricated to insure good and long life operation with minimum of trouble. This applies not only to the transmission that transmits power from the engine to the powered source but also transmissions which may be contained within the engine such as the drives for camshafts, balance shafts and the like.
The simplest form of transmission lubrication system is a splash system wherein lubricant is contained within the transmission casing and is circulated therethrough merely by the rotation of the gears within the transmission. However, this type of transmission requires the immersion of a substantial portion of the lower-most gears in the transmission in the lubricant. This can give rise to heavy drag.
If, on the other hand, the transmission is maintained at a low fluid level, then once the mechanism begins to operate there may not be adequate lubricant in the sump so that the lower-most gears will contact it.
It is, therefore, a further object of this invention to provide a simplified transmission lubrication system wherein adequate amounts of lubricant are contained but wherein the gears are not deeply submerged in the lubricant when running.
It is a further object of this invention to provide an improved splash-type transmission lubrication system wherein the lower-most gear is relatively deeply submerged when the transmission is not operating so as to afford a large lubricant capacity but wherein the lubricant is pumped into another cavity during running of the transmission so as to reduce drag.
With the so-called splash type of transmission lubrication systems, there is also a problem in insuring adequate cooling of the lubricant. It is, therefore, a still further object of this invention to provide an improved arrangement for cooling the lubricant in a transmission.